1. Technical Field
The present invention relates in particular to a travel control apparatus for a vehicle, with which a preceding vehicle in an identical lane can be overtaken using an automatic driving technique.
2. Related Art
Recently, various apparatuses employing automatic driving techniques that enable a driver to drive a vehicle in increased comfort and more safely have been developed and proposed. Japanese Unexamined Patent Application Publication No. 2011-162132, for example, discloses a technique employed in an automatic driving apparatus that performs automatic driving control to ensure that a vehicle follows a road on which the vehicle is traveling. In this technique, a vehicle equipped with the apparatus is controlled to change lanes to a travel lane after detecting that the lane in which the vehicle is traveling is an overtaking lane.
When a system failure (for example, a failure relating to acquisition of travel environment information or a failure in a steering system used to execute a lane change) occurs during automatic driving while an overtaking target vehicle ahead of the vehicle in the same travel lane is detected and overtaking control is executed to overtake the overtaking target vehicle using automatic driving control, there is a great need to return the vehicle automatically to the original travel lane using a technique such as that of the automatic driving apparatus disclosed in Japanese Unexamined Patent Application Publication No. 2011-162132. However, overtaking control is executed through a combination of complicated travel operations such as a lane change for the purpose of overtaking, acceleration following the lane change, and a lane change back to the original lane following overtaking acceleration, and unless failsafe control corresponding to conditions during each of the overtaking control operations is executed when the system failure occurs, it may be impossible to secure sufficient safety.